This invention relates to a clamp for a bag sealing machine and, more particularly, to a clamp which is uniquely mounted for cooperation with a sealing drum in developing a stream of plastic bags. Illustrative of the type of bag making machine with which this invention is concerned is my earlier U.S. Pat. No. 4,609,367. This utilized clamp bar assemblies to hold the polyethylene web against the sealing drum during the cutoff and cooling process. The cutoff process created the side seal of the individual bag. More particularly, the clamp bar assembly held the polyethylene web firmly to the sealing drum to prevent slippage during cutoff. The clamp bars themselves held the polyethylene on the leading and trailing edges of consecutive segments of the polyethylene web. A cutoff and sealing wire was moved on a path that allowed it to pass between the leading and trailing edges of the polyethylene web and clamps--to create the individual bags. Exemplary of the type of bag made on such machinery was the well-known reclosable bag which employed fastener strips of an interlocking nature.
The prior art machines, and those today, for that matter, generally run two-wide. In such machines, the clamp bar assembly consists of four clamping surfaces. Each clamping surface was allowed to pivot radially to align itself with the sealing drum surface. However, there was no provision for axially aligning the clamp bar. Since the clamp bars needed to clamp evenly across the entire clamping surface, considerable time was spent manually adjusting the axial alignment of the clamps. This procedure was labor intensive and required machine adjustments using feeler gauges and the loosening positioning and tightening of the clamp support bracket of each clamping surface. This was labor intensive in that it normally required shimming and adjusting numerous times the various clamp bars. The duration of this problem can be appreciated from the fact that it existed as early as the time of my earlier U.S. Pat. No. 3,640,050 which had to do with the portion of the machine employed for boxing the bags.
According to the invention herein, the problem has been solved by the seemingly simple expedient of doing away with the bolts that secure rigidly the clamp bars to the pivot shafts and instead providing a pivot pin connection therebetween with a slight amount of clearance between the pivot pin on one member and the pin receiving opening on the other member. This has resulted in a self-adjusting characteristic which is forgiving of the heretofore difficult tolerances.
Other objects and advantages of the invention may be seen in the details of the ensuing specification.